For as long as mobile phones have existed, mobile phone users have suffered from a typical problem. When users have phone conversations in a noisy environment, such as a moving car, a noisy bar or the like, it is very difficult to understand the other party. This is true even if the other party is in a quiet environment and is actually producing very high quality speech signals. The reason for this difficulty is that the human auditory system requires that an audio or speech signal is above a certain signal level relative to the ambient noise in order to achieve a minimum required intelligibility. Furthermore, it's generally understood in the art, that in order to feel comfortable with the conversation, humans require an even higher signal level that is well above the ambient noise level. While those qualitative terms are not easily quantifiable, this phenomenon can be easily demonstrated. For example, users will generally increase the volume of a radio system in a high velocity moving automobile in order to make them feel comfortable, even though such a volume would usually be perceived as being much too high when the car is stationary. Also, people will often shout at each other in a noisy environment in order to be able to hear their conversation over the ambient noise, when such a volume level would be much higher than the volume level of the same conversation taking place in a quieter environment.
From a user's perspective, mobile phones are designed and manufactured to maintain certain “fidelity” in reproducing the sound quality from a far-end caller. This fidelity assumes the user is carrying out the conversation in a relatively quiet environment such as in a home or office. Indeed, the Telecommunication Standardization Sector of International Telecommunication Union (ITU-T) defines a signal to noise ratio (SNR) of 20 dB or 15 dB as their “noisy” environment test condition for standardizing voice compression algorithms for use in telecom equipment, such as mobile phones. Unfortunately, in real life application scenarios, such a condition is not always guaranteed, and users often need to carry out conversations under much noisier conditions, and the perceived quality or quality of experience (QoE) is unquestionably deteriorated. Users' sole option today is to increase the volume of their mobile phones to the maximum, and if that still does not allow for a reasonable conversation to occur, they usually terminate the call prematurely as an unwanted consequence of this condition.
In the personal infotainment/communication industry, portable handheld products like the Apple iPod®, iPad®, Nintendo DS®, and Sony PSP® cause end-user's to suffer from the same ambient noise impairment that lowers their perceived QoE, as described above. When the ambient noise level is high, a user's only option presently is to increase the playback volume of the sound to the maximum capability of the device. Not only is this uncomfortable, but may also be harmful because young children, who are most likely to use this type of equipment, can suffer permanent damage to their developing auditory systems by constantly increasing the playback volume to the maximum capacity when in such noisy environments.
Accordingly, there is an intense need for a method that can perform the desired result of increasing a user's QoE in a noisy environment without necessarily resorting to simple volume increases.